Field of the Invention
The present invention relates to a constant-velocity joint, which is interposed between a first transmission shaft and a second transmission shaft, for transmitting rotary drive power from the first transmission shaft to the second transmission shaft.
Description of the Related Art
Automobiles are arranged such that rotary drive power, which is generated by an internal combustion engine, an electric motor, or the like, is transmitted to the tires by drive power transmission shafts such as drive shafts, etc. In this case, the automobile is driven when the tires are rotated by the transmitted rotary drive power.
A constant-velocity joint is interposed between the drive power transmission shafts. The constant-velocity joint interconnects the drive power transmission shafts, such that the drive power transmission shafts can rotate about respective axes thereof.
One known type of constant-velocity joint is a tripod constant-velocity joint. Such a tripod constant-velocity joint includes an outer member having a bottomed cup, and an inner member that is fitted to the distal end of a drive power transmission shaft. Rollers, which are held by holders of the inner member, slide while rotating within respective guide grooves defined in an inner wall surface of the bottomed cup. When the drive power transmission shaft is tilted at a prescribed working angle, the holders are tilted relative to the rollers within the guide grooves in response to the inner member being tilted within the outer member.
If the rollers are tilted in following relation to the inclination of the holders, slippage occurs between the wall surfaces of the guide grooves and the rollers, thus resulting in an increase in sliding resistance. To avoid this problem, a structure has been proposed in which the posture of the rollers with respect to the guide grooves is maintained even if the holders are tilted. For example, in Japanese Patent No. 3984816, a constant-velocity joint is disclosed, in which the inner wall surface of each roller (referred to as “a ring” in Japanese Patent No. 3984816) and the side wall surface of each holder are placed in contact on a region, whereas the inner wall surface of the roller and the side wall surface of the holder are spaced away from each other on another region whereby a clearance is formed at the other region. The contact location between the inner wall surfaces of the rollers and the side wall surfaces of the holders normally is set at the center in the widthwise direction of the rings. Further, the holders are capable of being tilted about the contact location.